1. Field of the Invention
The present invention relates generally an energy harvester for an implant device and to an implant device including such an energy harvester. The present invention also relates to an implant apparatus for implantation into a mammal, a method of implanting an implant apparatus into a mammal and a method of operating an implant apparatus that is implanted into a mammal. In particular, the present invention relates generally to the field of power generation within a biological living body, such as a mammal, using motions of that body to produce electrical energy, to power a variety of types of implant devices.
2. Description of the Prior Art
Current medical implant devices, such as pacemakers and defibrillators, rely heavily on electrical power to function for extended periods of time. However, current battery technology is the principal limiting factor to the life span of these devices, as battery capacity has reached a plateau, with recent developments in battery technology producing only marginal increases in storage capacity to volume ratios.
Some implanted devices are able to be recharged through the use of induction loops implanted subcutaneously. By coupling an implanted loop to an external induction re-charger, an implanted device can be recharged to extend it operational life. This, however, requires the patient to monitor the power levels of the implanted device and to position the induction re-charger at regular intervals, to ensure the device is kept charged.
Not only is this time consuming for the patient, but is also inefficient in its power use, as a large proportion of the energy used to power the induction loop is lost due to heating and magnetic field fringe effects. Inefficiencies are also experienced by misalignment of the two induction loops, reducing the coupling efficiency of the power transmission.
This technique can also produce levels of psychological stress within the patient, with regards to the anxiety of a power failure of the implanted device.
It has been thought that an implantable generator, which uses motions of the body to produce power for implanted devices, would be of significant interest to the medical implant industry and so of commercial value to the entity that could produce such a generator.
US-A-2005/0256549 discloses a micro-generator implant device including (a) a micro-generator, disposed within a living body, the micro-generator including: (i) a first mechanism for harnessing mechanical energy from a natural body movement, and (ii) a second mechanism for converting the mechanical energy to electrical energy, the electrical energy for providing power within the living body. In particular, this specification discloses a great many energy harvesting techniques, employing (a) motion of heart muscle tissue; (b) motion of blood passing through a blood vessel; or (c) motion of a limb, or of the entire body as the source of mechanical energy. All of these proposals suffer from the problems of technical complexity and/or the requirement for an invasive surgical procedure and/or long term reliability and/or the possibility of secondary medical problems. For example, the use of the motion of blood passing through a blood vessel requires a complicated rotating mechanism, namely a “watch mechanism”, to be implanted into an artery.
The present invention aims at least partly to overcome these problems of the known implant devices and the energy source therefor.